MY STARTING point must be the traditional Christian view that each soul is created with its body, that each soul is unique and that we have only one earthly existence. So the catechism of the Catholic Church says that "every soul is created immediately by God... and... it is immortal".

The Roman Catholic Church also teaches that from the moment the ovum is fertilised we have the life of a new human being, a person, a spiritual soul, even if this cannot be ascertained by empirical data.

The implications of this are obvious. In considering the possibility of abortion, even the morning-after pill, and embryo research, we are considering what might or might not be done to a human soul.

A modern scientific view, however, approaches the question of the beginning of life rather differently. On this perspective, consciousness - our capacity to feel, think and choose, to remember and hope - is integrally related to the brain. We know that there is a correlation between conscious activity and impulses in the brain and that if part of the brain is affected by accident, illness, drugs or an operation, the way we feel, think and act can be decisively affected.

However, there are a number of reasons why this form of the "identity theory", according to which the mind (or soul) and the brain are identified, should be subjected to sceptical scrutiny. A fundamental assumption of rational discourse is that we can approach, even if we can never fully comprehend or grasp, the truth of things. The search for the truth about the relationship between mind and brain presupposes that however integral the one is to the other, there is a realm of the mind with its own validity and liberty.

However, I believe that we should fully accept all assured scientific findings that relate consciousness to what happens in the brain and nervous system. This does not mean that consciousness is reducible to those electrical impulses. On the contrary, consciousness has evolved because it has a distinct function in helping human beings to adapt and survive. There is a realm of mental activity which enables us to do that, one which is itself the cause of brain movements rather than their effect. This mental realm, though integrally related to the brain and body in this life, could in principle be expressed in other ways, through other media, which is what Christians mean when they talk about the resurrection of the body.

Secondly, I suggest that if we see consciousness as an emerging entity in this way, dependent on the brain having evolved to a certain point both in the evolutionary process itself and in the life-cycle of the individual, we need to be circumspect in talking about the souls being immediately created by God at conception or some point shortly afterwards.

We cannot, for example, think of souls as independent spiritual realities implanted by God. Rather, soul language points to a central truth about our humanity, that we are oriented towards God and shaped for immortality. To say that our souls are created immediately by God is to highlight each unique individual existence and its spiritual status.

And finally, I believe, using the basis of the Church's teaching until the 19th century, that while the embryo should be protected, it cannot be accorded the moral status of an adult or newly born baby. The implication of this, of course, is that abortion in the early stages of pregnancy and research on embryos up to 14 days old, cannot be absolutely debarred on moral grounds.

There may, indeed, be grave and good reasons for an abortion under certain circumstances. There may also be overridingly good reasons to do with human fertility or advancing scientific knowledge that would greatly benefit humanity, why research should be carried out. Nor should we think of this as simply a cowardly concession to the spirit of the age. It is good that we can interact with nature, as God's co-workers, in bringing about the health which he wills for humanity and the healthy children that he desires.

In short, this is something positive we can say with confidence and not just on the defensive. But even more positive is our vision of what it is to be a human being. We can look at human beings from many different points of view. We are a mixture of the physical and the spiritual, the mortal and the immortal. We are as fragile and passing as potsherd and matchwood. But all the time we are also an immortal diamond - a person, being shaped towards God and for God. In the end, this is what we are called to be, and through Christ can be. When all else has served its purpose and falls away, we are immortal diamonds.